Feedback channels are also designed for the pile release mechanism 

 (Foundation/Anchorage Subsystem), an attitude sensor, and two pressure 

 sensors. One of the pressure sensors would be a pressure release valve 

 to prevent excessive system pressures. The second sensor would be used 

 to indicate a given level of torque at the piles. The torque level can 

 be chosen arbitrarily. However, it would probably be a torque corre- 

 sponding to the estimated lateral resistance of the two stationary piles 

 during the initial phase of pile emplacement. If the sensor indicated 

 that the torque might overcome the reaction forces , driving of the pile 

 could be discontinued until the other piles were emplaced deeply enough 

 to resist the torque. 



Many other control and feedback functions are possible and would 

 be valuable, but the cost of providing additional functions is believed 

 to be too great to be justified for the pilot-model system. Testing 

 with the pilot model will determine the need for additional control or 

 feedback in a prototype system. 



Loading Handling and Surface Support Subsystem 



This subsystem includes the surface vessel, the E-M cable, the 

 winch, handling slings, shipboard cranes, and related items. As 

 previously indicated (Operating Requirements) the overall system will 

 require a minimum of 500 square feet of deck space and a 20-ton crane 

 for over-the-side handling. This definitely limits the vessels from 

 which the system can be operated since few "ships-of-opportunity" have 

 installed, or can support, a 20-ton crane. 



It is expected that the system will be lowered with either the NCEL 

 seafloor deep corer winch or the NCEL motion-compensating winch. The 

 E-M cable for the NCEL deep corer could be utilized for the pile emplace- 

 ment system, or a new cable with a minimum 80,000-pound breaking strength 

 could be designed and purchased. The decision concerning a new cable must 

 be made during final design of the control and feedback system on the 

 basis of a trade-off study of the relative costs of adapting the controls 

 to the corer E-M cable versus providing a new cable. 



SIMPLIFIED, LIMITED-CAPABILITY SYSTEM FOR ANCHORAGES 



In the course of developing the preliminary design presented 

 herein a concept for a simplified system with a limited capability 

 evolved^. If the requirements for vertical downward load capacity and 

 lateral load capacity are eliminated the cross-section dimension of the 

 pile can be reduced because the buckling resistance of the 10 by 10-inch 

 cross-section is no longer required. The system becomes an uplift- 

 resisting anchor. By using a 4 by 4-inch cross-section the required 

 installation torque is approximately halved. If the rotation rate is 

 also reduced from 10 rpm to 2 rpm the horsepower requirement is reduced 



19 



